Well, first some forums advice, the off topic section is shared with many other game forums that are published by stardock (not just sins), so you should probably put threads like this in the modding or general section.

As for your question, the Galaxy Forge requires that you have the .NET framework (at least 3.5), and this is usually the reason why people can't run it correctly. In fact you can use the Galaxy Forge without having Sins or Entrenchment on your computer anyways!

While they're at it, they should add "RandomMilitia" and "Pirate" to the spawn as category. It a same to have such a beautiful GUI mapmaker and still have to do some things in TXT format.

Also, the Forge is very much behind in terms of having support for all the planet bonuses and artifacts, but I've added them myself if anyone wants them.

Right click on the galaxy forge and hit properties. What type of file is it? It should say application. If it does then for some reason your computer can't figure out how to run .exe's and that just shouldn't happen. Though again, make sure you have your .NET framework updated! (to at least 3.5)

then it needs to be unzipped, find an unzip application, there are a million of them and unzip it

How do i unzip it